Hydraulic drive system for press brakes



June 28, 1966 E. HNNI HYDRAULIC DRIVE SYSTEM FOR PRESS BRAKES\\\\\\\\\\\w nmflwm United States Patent O 3,257,810 HYDRAULIC DRIVESYSTEM FOR PRESS BRAKES Eduard Hnni, Rosengartenstrasse 10, Zofingen,Switzerland Filed Sept. 10, 1964, Ser. No. 395,473 Claims priority,application Austria, Sept. 12, 1963, A 7,339/ 63 2 Claims. (Cl. 60-54.5)

This invention relates to a hydraulic drive system for press brakes,and' particularly to a hydraulic drive system for a press 'brake inwhich an elongated beam is moved toward and away from a press bench inparallel alignment by means of two pistons or groups of pistonsrespectively engaging the end of the beam.

It is the object of this invention to provide a hydraulic system for apress brake of the type described in which parallel movement of thepress beam relative to the bench is achieved in a simple and reliablemanner.

A primary feature of the system of the invention is a pressuremultiplier which is connected to a source of liquid at relatively lowpressure and supplies liquid at higher pressure to the pistons whichactuate movement of the press beam.

Other objects and features of the invention will become apparent tothose skilled in the art from the following detailed description of apreferred embodiment of the invention as illustrated in the accompanyingsheet of drawing whos-e sole figure shows the hydraulic system of apress brake partly in a conventional manner, and partly in elevationalsection.

Referring to the drawing in detail, there is shown a motor 1 which iscoupled to a pump 2. The dischar-ge line 35 of the pump is equipped witha safety valve 3 and is connected to a three-way control valve 4. In theillustrated normal position of the valve, the discharge .line 35communicates with a sump 10 through a return line 9, while a line 11which leads from the valve 4 to a pressure multiplier 8 is blocked.

The valve 4 is electrically operated in a conventional manner bysolenoids 4', 4 controlled by limit switches 37, 38 on the press. Whenthe valve 4 is shifted toward the left from the illustrated position,fluid under pressure from the pump 2 enters the line 11. .If the valve 4is shifted to the right from the illustrated normal position, the lines11 and 35 are both connected to the return line 9.

The pressure multiplier 8 has a cylinder cavity which is divided intotwo coaxial compartments 12, 13 by a partition 16. The cross section ofthe compartment 12 is somewhat smaller than that of the compartment 13.Pistons 14, 17 respectively arranged in the compartments 12, 13 areconnected lby a common piston rod 15 which passes through the partition16. The piston 17 has an annular face 18 about the rod 15, in a circularface 19.

Four axially elongated bores 20 communicate with the compartment 13 andare angularly spaced about the axis of the multiplier 8. Plungers 21 arerespectively received in the bores 20 and normally abut against the face`19' of the piston 17. Only two of the 'bores 20 and the associatedplungers 21 are visible in the drawing.

The two hydraulic cylinders 24, 25 which are connected to the pressbrake, not itself shown, near the ends of the beam, communicate withrespective pairs of bores 20 by pressure lines 22, 23 equipped withcompensating valves 36. A piston 33 is axially movable in each cylinder24, 25. A stop 34 is arranged in each cylinder 24, 25 and is adjustabletherein in a non-illustrated manner.

The control circuit of the pressure multiplier 8 further includes aplunger valve 26 and an auxiliary valve 27 which is electricallyoperated by a solenoid 27' and a limit switch 39, and is shifted intothe illustrated position Patented June 28, 1966 ice when the brake beamreaches a certain position to close the switch 39.

The line 11 is permanently connected with a conduit 28" in themultiplier 8 which connects the portion of the compartment 13 adjacentthe annular piston face 18 with the plunger valve 26. The valve 26 isalso connected with the compartment 12 by a conduit 28', and with theauxiliary valve 27- by a conduit 31. The movements of the plunger 26 inthe valve 26 are actuated by admission and release of fluid through aconduit 29 connected to the auxiliary -valve 27'. The last mentionedvalve is also connected with the conduit 28 by a line 30, and with asump 32.

The aforexlescribed hydraulic system is operated as follows:

The valve 4 is shifted toward the left so that hydraulic fluid ows fromthe discharge line 35 into the compartments 12, 13 through the line 11,the conduits 28', 28", and the open plunger valve 26.

Because the piston face 18 is greater than the corresponding annularface of the piston 12, the two pistons 14, 17 ymove rapidly in thedirection of the arrow 34 under the small force exerted by fluid on theexcess area of the piston face 18. As long as the press beam can movefreely, it is quickly moved toward a work piece by the pistons 33.

The limit switch 39 is actuated by a moving element of the press brake,not itself shown, and triggers movement of the auxiliary valve 27 intothe illustrated position. Pressure uid from the pump 2 is admitted tothe conduit 29 by the valve 27, and the plunger-26' moves toward theright from the illustrated position to block Ithe orice of the conduit28. The conduit 28" is simultaneously vented to the sump 32 by the valve27. The full pump pressure acts on the frace 18 of the piston 17 whereasthe piston 14 is relieved of fluid pressure.

The pistons 33 perform their power stroke under the pressure of fluiddriven from the bores 20 by the plungers 21, and engage the stops 34. Ifunequal oil leakage from the two cylinders 24, 25 causes one piston 33to engage its stop 34 before the other piston, the resulting highpressure in its associated pressure line 22 or 23 opens the compensatingvalve 36 in the line, and the amount of fluid in the twol hydraulicsystems associated with the cylinders 24, 25 is balanced. Thisadjustment and' balancing occurs automatically during each operatingcycle of the press brake.

When the control valve 4 is shifted toward the right, the pump dischargeline 35 and the line 11 are connected to the sump 10.

The return arrangement which biases the press beam upwardly away fromthe 'bench causes the pistons 33 to expel fluid from the cylinders 24,25. The plungers 21 move the pistons 14, 17 toward the illustratedposition, and oil is displaced from the compartment 13 through theconduit 28, the lines 11 and 9 into the sump 10.

When the valve 4 returns to its normal illustrated position, the pumpdischarge line 35 is connected with the sump 10, and the line 11 isblocked.

The pressure multiplier and the associated elements thus provide highfluid pressure for operation of the press beam from a motor-driven pumpwhich generates relatively low pressure. The parallel alignment of thepress beam with the bench is automatically maintained. When the pressoperates against low resistance, the press beam is moved at high speed.

What is claimed is:

1. A hydraulic system comprising, in combination:

(a) a source of hydraulic fluid at relatively low pressure;

(b) two hydrauliccylinder means adapted to be connected to the two endsof a press brake beam;

(c) pressure multiplier means interposed between said source and saidcylinders for supplying fluid at relatively high pressure to saidcylinder means in response to the low pressure of the fiuid from saidsource, said pressure multiplier means including (1) means definingfirst and second cylinder compartments,

(2) a first piston and a second piston movably received in saidcompartments respectively, the effective piston area of said firstpiston being greater than the effective piston area of said secg ondpiston,

(3) means defining first and second bores communieating with said firstcompartment (4) a first plunger and a second plunger movably received insaid bores respectively and engageable with said first piston when thesame moves in said first compartment in a predetermined direction todrive said plungers inward of the associated bores, and

(5) motion transmitting means fixedly connecting said first andsecondpistons for joint movement;

(d) valve means for connecting said source to said compartments, saidvalve means including a plurality of valve members movable relative toeach other between (i) a first position in which said source issimultaneously connected to said compartment for applying the lowpressure of said fiuid thereof to said first piston in a manner to movesaid first and second pistons jointly in said predetermined direction,and to said second piston in a manner to move said first and secondpistons jointly in a direction opposite to said predetermined direction,whereby said pistons jointly move in said predetermined direction,

(ii) a second position in which said'source is connected to said firstcompartment for moving said pistons in said predetermined direction,while said second compartment is vented, and

(iii) a third position in which said first and second compartments arevented;

(e) two pressure lines respectively connecting said bores to saidhydraulic cylinder means; and

(f) two compensating valve means respectively communicating with saidpressure lines and responsive to a predetermined pressure therein forbleeding the associated pressure line,

(1) each hydraulic cylinder means including a cylinder membercommunicating with the associated pressure line, a piston member movablein said cylinder member in response to fluid pressure in said pressureline, and a stop mem- -ber arranged iin :the cylinder member forlimiting the movement of said piston member.

2. A system as set forth in claim 1, wherein said valve means include afirst valve having a plurality of connections respectively communicatingwith said source, with said iirst compartment, and with the atmosphere,a second valve interposed between said compartments, valve actuatingmeans for moving said second valve between an open position thereof inwhich said second valve connects said compartments and a closedposition, and a third valve operatively connected to said valveactuating means for venting said second compartment when said secondvalve is in said closed position.

References Cited by the Examiner UNITED STATES PATENTS 354,014 12/1886Easton 91-165 X 1,084,512 1/1914 Weikel 91-165 X 1,239,862 9/1917 Baird92--152 X 1,970,999 8/1934 Ferris et al. 6054.5 2,030,966 2/1936 Craneet al 60-52 2,032,185 2/1936 Sciaky 60-54.5 2,058,377 10/1936 Francis60-54.5 X 2,308,712 1/1943 Peterson et al. 60-54.5 2,472,236 6/1949Thomas 92-152 X 2,507,868 5/1950 -Purcell 60-52 2,608,059 8/1952 Kux60-54.5 2,915,878 12/1959 Hramoff 60-54.5 2,916,205 12/1959 Litz 92-152X FOREIGN PATENTS 1,099,682 3/1955 France.

560,678 4/ 1944 Great Britain.

SAMUEL LEVINE, Primary Examiner.

ROBERT R. BUNEVICH, Examiner.

1. A HYDRAULIC SYSTEM COMPRISING, IN COMBINATION: (A) A SOURCE OFHYDRAULIC FLUID AT RELATIVELY LOW PRESSURE; (B) TWO HYDRAULIC CYLINDERMEANS ADAPTED TO BE CONNECTED TO THE TWO ENDS OF A PRESS BRAKE BEAM; (C)PRESSURE MULTIPLIER MEANS INTERPOSED BETWEEN SAID SOURCE AND SAIDCYLINDERS FOR SUPPLYING FLUID AT RELATIVELY HIGH PRESSURE TO SAIDCYLINDER MEANS IN RESPONSE TO THE LOW PRESSURE OF THE FLUID FROM SAIDSOURCE, SAID PRESSURE MULTIPLIER MEANS INCLUDING (1) MEANS DEFININGFIRST AND SECOND CYLINDER COMPARTMENTS, (2) A FIRST PISTON AND A SECONDPISTON MOVABLY RECEIVED IN SAID COMPARTMENTS RESPECTIVELY, THE EFFECTIVEPISTON AREA OF SAID FIRST PISTON BEING GREATER THAN THE EFFECTIVE PISTONAREA OF SAID SECOND PISTON, (3) MEANS DEFINING FIRST AND SECOND BORESCOMMUNICATING WITH SAID FIRST COMPARTMENT (4) A FIRST PLUNGER AND ASECOND PLUNGER MOVABLY RECEIVED IN SAID BORES RESPECTIVELY ANDENGAGEABLE WITH SAID FIRST PISTON WHEN THE SAME MOVES IN SAID FIRSTCOMPARTMENT IN A PREDETERMINED DIRECTION TO DRIVE SAID PLUNGERS INWARDOF THE ASSOCIATED BORES, AND (5) MOTION TRANSMITTING MEANS FIXEDLYCONNECTING SAID FIRST AND SECOND PISTONS FOR JOINT MOVEMENT; (D) VALVEMEANS FOR CONNECTING SAID SOURCE TO SAID COMPARTMENTS, SAID VALVE MEANSINCLUDING A PLURALITY OF VALVE MEMBERS MOVABLE RELATIVE TO EACH OTHERBETWEEN (I) A FIRST POSITION IN WHICH SAID SOURCE IS SIMULTANEOUSLYCONNECTED TO SAID COMPARTMENT FOR APPLYING THE LOW PRESSURE OF SAIDFLUID THEREOF TO SAID FIRST PISTON IN A MANNER TO MOVE SAID FIRST ANDSECOND PISTONS JOINTLY IN SAID PREDETERMINED DIRECTION, AND TO SAIDSECOND PISTON IN A MANNER TO MOVE SAID FIRST AND SECOND PISTONS JOINTLYIN A DIRECTION OPPOSITE TO SAID PREDETERMINED DIRECTION, WHEREBY SAIDPISTONS JOINTLY MOVE IN SAID PREDETERMINED DIRECTION, (II) A SECONDPOSITION IN WHICH SAID SOURCE IS CONNECTED TO SAID FIRST COMPARTMENT FORMOVING SAID PISTONS IN SAID PREDETERMINED DIRECTION, WHILE SAID SECONDCOMPARTMENT IS VENTED, AND (III) A THIRD POSITION IN WICH SAID FIRST ANDSECOND COMPARTMENTS ARE VENTED; (E) TWO PRESSURE LINES RESPECTIVELYCONNECTING SAID BORES TO SAID HYDRAULIC CYLINDER MEANS; AND (F) TWOCOMPENSATING VALVE MEANS RESPECTIVELY COMMUNICATING WITH SAID PRESSURELINES AND RESPONSIVE TO A PREDETERMINED PRESSURE THERIN FOR BLEEDING THEASSOCIATED PRESSURE LINE, (1) EACH HYDRAULIC CYLINDER MEANS INCLUDING ACYLINDER MEMBER COMMUNICATING WITH THE ASSOCIATED PRESSURELINE, A PISTONMEMBER MOVABLE IN SAID CYLINDER MEMBER IN RESPONSE TO FLUID PRESSURE INSAID PRESSURE LINE, AND A STOP MEMBER ARRANGED IN THE CYLINDER MEMBERFOR LIMITING THE MOVEMENT OF SAID PISTON MEMBER.